It's worth noting that men are typically trained to look to sexual/romantic partners (i.e., women they are not related to) for emotional support, not to their friends or family members.
It's horrible and confusing for the female partner of such a man, because women are taught completely different rules about how to access support. But I think for a lot of men who are going through serious things, a non-related woman is easier to open up to/feel attachment to. This causes a risk of physical affairs, for sure, but can also be expressed as platonic friendships, sometimes in which there is a (often unrequited) crush involved.
Basically you may have a man in emotional distress, feeling absolutely unable to lean on anyone because he's supposed to be strong etc, spending time with an unrelated woman and over time feeling that he can lean on her at least a little. He may become really attached to that woman.
We can go on about how he should just focus on his relationship or lean on friends or family, yes, those are great points, but also this guy was suicidal, with an abusive partner who was going through a bereavement. He's not going to make great choices. That's the reality of how life happens.
I appreciate that we like black-and-white rules around here, but in reality, it's all shades of grey and even moreso when there is suicidal ideation, abuse, bereavement, and the reality that patriarchy cuts both ways, it limits men's lives and choices as well as women's, just in different ways. Compassion is needed on all sides imo.